Anyone who saw San Andreas last month knows it's just a matter of time before the movie's eponymous fault line brings about the worst disaster in US history -- except they're only half right.
There is a potentially dangerous fault line on the West Coast, one we should be immediately worried about, but it's not the San Andreas. It's called the Cascadia Subduction Zone, and seismologists believe it's long overdue for an apocalyptic shake-up.
The Cascadia Subduction Zone gets its name from the Cascade Mountain Range, and the "subduction zone" part essentially means it's an area where two tectonic plates meet, and one slides beneath another. According to scientific estimates, the CSZ experiences a magnitude 8-9 earthquake every 200-500 years, and as luck would have it, we're about 300 years out from the last one. That means the next event could happen within the next century, or as soon as 50 years from now.
As Kathryn Schulz explains in her fascinating New Yorker piece (bookmark that), FEMA estimates a magnitude 8 or 9 CSZ earthquake -- and the ensuing tsunami -- could result in nearly 13,000 deaths (40,000 total casualties). That insanely high number comes courtesy of the fault's size and location (running alongside Northwestern California, all of Oregon and Washington, and nearly half of Vancouver Island).
Nobody even knew the Cascadia Subduction Zone existed 45 years ago -- now, though, seismologists and geologists are closely monitoring the CSZ, and both the state and federal governments are beginning to take steps toward averting the disaster of a catastrophic earthquake in the northwestern United States. As for whether it'll be enough, well we'll find out in 50 years.